Ore burner



Julyf 27, 1937.

R. B. FERGUSON ORE BURNER Filed March 28, 1936 -INVENTQR bert B. Ferguson ATTORNEY s `Patented .July 27, 11937 *ORE BURNER Robert B. Ferguson, Plainfield, N. J., assignor to General Chemical Company, New York, N. Y., a corporation of New York Application March 28, 1936, Serial No. 71,405

3 Claims.

VThis invention is directed to an apparatus for roasting metal sulfldes, and more particularly for roasting finely divided sulfldes vto desulfurze the same and to produce sulfur dioxide for use 5 in the manufacture of sulfuric acid, or' for any other purposes desired. The invention is particularly related to roasters having a hoppered or tapered hearth for collection and discharge 'of cinder.l

In operating roasters of the character described there is occasionally a tendency for the cinder on the hearth to cohere or cake, particularly when such a roaster is operating at high capacity; Furf ther, under some operating conditions there is a tendency for the cinder to build up on the sloping sides of the hearth and it thus becomes necessary from' time to time to loosen by a bary the cinder from the hearth. However, the hearth of such a burner may be too large to permit the operator to reach conveniently with a bar all parts of the hearth through the cinder outlet or through a work hole. According to the present invention the bottom is so constructed that the entire hearth can be reached readily.

Other and further objects and advantages of the invention may be fully understood from a consideration of the following description taken in connection' with the accompanying drawing, whichis a vertical section of a preferred lform of roaster showing the improved hearth.

Referring to the drawing, the shaftroaster shown comprises a cylindrical shaft I0, compris' ing-a steel shell or casing I I and fa furnace lining I2 placed therein, constructed of suitable refractory material such as flrebrick and defining a roasting chamber I4 of circular horizontal'section. The upper part of the roasting chamber is closed by a crown I5, the top'side of which forms a drying or preheating `hearth I1.

The shell II .projects upwardly beyond the crown I5. The surface of hearth I1 slopes downwardly toward the shell of. the burner. Lying above the hearth rare rabble arms I9, carried and driven by a hub 26 supported bya xframework, not

shown, and having downwardly projecting plows 2| pitched' to work suliides, fed to the center of 'the hearth I1, gradually toward the circumference of the' drying hearth.A

Attached toshell II `by suitable `brackets not shown 'are hoppers 22 covered by sloping screens 23. Cut through the shell I I and also in the upper edge of lining I2 are downwardly sloping passages or conduits 24 through which fines are passed from` drying hearth I1 into hoppers 22.

55 Oversized material discharged byl screens' 23 is collected by receptacles 25 and conveyed by means not shown toa crusher, or used in va bed roaster or otherwise disposed of. It will be understood that the number of conduits 24 and hoppers 22 used in conjunction with the roaster 5 .correspond with the number of ore injectors 26 employed. On rotation of rabble arms I9 the sulfide fines are gradually' fed through openings 24 into hoppers 22 which discharge fines into injector feed pipes 21 having at their lower endslO any suitable -means such as slide `valves 28 for controlling flow of nes out of the lower ends of pipes 21. y

Each ore injector 26, shown more or less diagramrnatically in the drawing, comprises princil5 pally an elongated pipe section or nozzle 29 constituting a fines inlet conduit. A pipe 3U, carrying on the upper end a funnelv 3i, is arranged to feed fines into the lower end of nozzle 29. Air or other gas used to inject the fines into the burner is 20 supplied from a bustle pipe 32 surrounding the lower end of the burner. Bustle 32- may bev convnecteci to a blower or other source of air through pipe 33. Adjacent injector 26, pipe 32 is provided with an air outlet nipple 3,4 connected by a con- 25 trol valve to a flexible hose connection which is attached at-the other end to nozzle 29. Each injector 26 may be supported by a suitable bracket, not shown, so that the upper end of the nozzle 29 extends through an opening 35 in the shaft IIJ 30 into the roasting chamber I4. The burner may be provided with any suitable Ynumber of injectors. In the embodiment illustrated, five injectors 26 are employed. Spaced about the lower end of the shaft I0 are air inlet pipes 36 through which air to support the combustion is introduced. The lower ends of the pipes 36 are connected to the bustle pipe 31 surrounding the lower end of the burner. Air is admitted to the pipe 31 and thence to the roasting 40 chamber I4 from pipe 38.

The hearth of the burner comprises a plurality of superposed frusto-conical sections 39, 40 of suitable refractory material. The upper section 39 isv attached to the lower edge of the shaft I0. 45 Spaced about the lower end of the shaft I0 and therethrough are openings 4I closed by doors 42.

. The sections 39 and 4I) are connected'by a cylindrical wall 43` through which wall are spaced openings 44 closed by doors 45. By operating 50 with a bar through the openings 4I and 44, cinders which have collected on sections 39 and.

40 may be loosened. Slightly below the openings 4I a platform 46 is provided, about 'which is a guard rail 41, and upon which an operator may 55 stand while loosening cinders from hearth 39. To remove cinders from the lower end of section 4II there is provided at the lower end thereof a pit 48 in which is a conveyor 49, which, in the embodiment shown, is of the drag-chain type, by which the cinders are removed through the opening 50.

A gas main 5I, for withdrawing the gaseous products of combustion from the burner, opens into the combustion chamber I4 at a point just below crown I5.

The invention is applicable to the roasting of finely divided metal suldes such as iron pyrites, pyrrhotite, zinc sulfide or arsenopyrite, but for convenience the operation of the process may be described in connection with the roasting of iron pyrites.

Before roasting is begun, roasting chamber I4 is preheated to temperatures above the ignition point of the particular ore to be roasted, as by the use of oil burners inserted through openings 4I. When the desired temperature` is obtained in the roasting chamber, rabble arms I9 may be rotated at a rate of, say, one revolution in two minutes. During rotation of rabble arms I9, the sulfide fines delivered to the center of hearth I1 are gradually worked across the hearth I1 and into the several passages 24, each of which communicates with a hopper 22. Thedry ordry and ployed to charge the fines into the combustion chamber. For this purpose it is preferred to employ air which may be admitted to the lower ends of nozzles 29 at pressures of, for example, about 5 pounds per square inch. The dotted line 54 indicates the approximate path of travel of an ore particle ofy average size introduced through the injector on the left side of the roaster.

The major portion of the total quantity of air, or other oxidizing gas, necessary to support the oxidation reaction either may be forced into the roasting chamber through the pipes 36, 31 and 38 or it may be drawn in through said pipes by exhausting gases from the chamber through the gas main 5I. When airais employed for injecting the fines through nozzles 29 not more than about 10% of the total air required for the oxidation need be introduced through the injectors 29, although larger amounts may be used if desired.

Following ignition, the fines rise to approximately the top of the roasting chamber, the temperature of the particles increasing because of rapidly progressing roasting. Although the air introduced is initially at about normal temperatures, the roasting operation is such thatthe temperature of the roasting atmosphere increases at a relatively uniform rate until the temperature 0f the gases in the top Qt the roasting chamber,

n entering gas main BI, may be about .1800-2000 F. Gas main` 5I may be connected to the inlet side of a blower so that the burner may operate under a slight negative pressure.

Due to the introduction of air at the lower end of the roasting chamber there is at the lower end a none of' substantially pure air through which the fines pass, which produces an iron oxide cinder. 'Ihis cinder, which then deposits upon the sections 39 and 40, is generally finely divided' and free-flowing, so that it runs into the pit 48, whence it is removed by conveyor 49. As above' indicated, however, there is occasionally la tendency for the cinder to cake or at least lose itl free-flowing character. At intervals, therefore, an operator may loosen the cinder on the sections 39 and 4|) with a bar by operating through the openings 4I, 44. -v

While a cinder collecting hearth having but two sections has been described, it is obvious that any number of sections may be employed depending upon the size of the roasting chamber.

I claim:

1. An ore roaster of the suspension type comprising a shaft in which the ore is adapted to be roasted while in gaseous suspension, and a cinder collecting hearth at the lower end of said shaft, said hearth comprising a plurality of inwardly inclined sections in stepped relation, the upper edge of each section but the topmost being adjacent the lower edge of the section next thereabove,

lthe upper edge of the topmost section being adjacent the llower edge of -said shaft, said ore roaster being provided with an opening at the upper edge of each section arranged to permit insertion of a bar to loosen cinder from the section there beneath.

2. Anore roaster of the suspension typ comprising a combustion chamber in which the ore is adapted to be roasted while in gaseous suspension, the lower end of said roaster comprising a downwardly and centrally converging cinder collecting hearth, said hearth being formed of a plurality of hollow frustoconical sections in stepped relation to convey cinder on any section to the lower end of the lowermost section. said sections being spaced apart between adjacent ends of adjacent sections an opening adjacent the upper edges of said sections for the insertion of a bar by which cinder may bev loosened from said hearth, and means at the lower end of the lowermost section to withdraw cinder therefrom.

3. An ore roaster comprising a shaft forming a combustion chamber in which ore is adapted to be roasted while in gaseous suspension, means including an injector passing through a side wall of said shaft for forming a dispersion of ore in the upper end of said combustion chamber, and a cinder collecting hearth at the lower end of said shaft, said hearth comprising a plurality of inwardly inclined sections in stepped relation, each section being provided with an opening at the yupper edge thereof and said stepped relation so spacing said sections vertically that access may be had through each opening to loperate a bar on the section next therebelow.

ROBERT B. FERGUSON. 

